1. Field of the Invention
The present invention relates to a mechanism for driving spindles in a ring spinning frame. More particularly, it relates to an improved unit driving mechanism applied to drive spindles of in a ring spinning frame.
2. Description of the Related Arts
In the driving of spindles of a ring spinning frame, the ring spinning frame must be driven in such a way that the consumption of electric power thereby is lowered, to reduce operating costs. A problem arises, however, of how to reduce variations in the rotation speed of the spindles, because such variations of the rotation speed of the spindles creates variations of the yarn quality at different spindles. Accordingly, it is essential to reduce the variations of the rotation speed of the spindles, to produce yarns having a good quality. This problem is particularly important when producing yarns by a large ring spinning frame provided with 900 spindles, or by a high speed ring spinning frame at which the rotation speed of the spindles is higher than 20,000 rpm. This is because, in the former case, the number of spindles is larger than that of the conventional ring spinning frame, and in the latter case, the yarn length produced in a unit time/spindle is larger than that of the conventional ring spinning frame.
To solve the problem of an increase of the electric power consumption, which raises the production costs, an improved driving mechanism applied to a ring spinning frame which is provided with a known tin pulley driving mechanism or a known tangential driving mechanism has been disclosed. For example, as shown in the invention disclosed by Japanese Unexamined Patent Publication No. Showa 63(1988)-243336, all of the spindles of a ring spinning frame are divided into a plurality of unit groups of spindles, wherein each unit group of spindles consists of two sub-groups of spindles aligned at both sides of a machine frame, respectively, in a condition such that the spindle alignments of the sub-groups at both sides of the machine frame face each other, and the spindles of each unit group are driven by a single drive mechanism. This single driving mechanism applied to unit groups of spindles partially solves the above-mentioned problem existing in a conventional driving system such as the tin pulley driving system. In the tangential driving system, however, it has been recognized that the problem of a reaction to the other spindles, due to the braking action applied to a spindle of a unit group of spindles by a knee brake, which is operated when a spinning yarn of the spindle concerned is broken, cannot be neglected when wishing to maintain the yarn quality. This problem is such that, when the braking action by a knee brake is applied to a spindle of a unit group of spindles driven by a single drive mechanism provided with an endless spindle tape, the spindle tape is elastically deformed by this braking action in the longitudinal direction thereof, and accordingly, the rotation speed of the other spindles of the unit group of spindles is varied. This variation of the rotation speed of the other spindles of the unit group of spindles has been confirmed by mill tests, and it has been recognized that such variations of the rotation speed of the spindles creates variations of the yarn twists, which is a serious problem when wishing to maintain the yarn quality in a good condition. Since a plurality of spindles of each unit group are driven by a single endless spindle tape, it is impossible to eliminate the above-mentioned variation of the rotation speed of spindles. Therefore, attempts have been made to maintain the variations of yarn twists in an allowable condition by keeping the above-mentioned variations of the rotation speed of spindles low. Generally, the allowance for the variations of yarn twists should not exceed 1%, and therefore, a desirable production policy is such that the variations of the rotation speed of spindles in each unit group of spindles when applying the knee brake to a spindle of the unit group of spindles should not be more than 1%.
As mentioned above, it is generally recognized by the normally skilled person in the spinning industry that the rotation speeds of the other spindles of a unit group spindles are varied when the knee brake is operated to brake the rotation of a particular spindle of an identical unit of spindles, but has not been clarified how the position of the other spindles in their respective relationships to the position of the above-mentioned particular spindle influences the reduction of the rotation speed of the other spindles.
On this point, if the above-mentioned phenomenon could be analyzed, it might be clarified that, regarding the rotation speed of the other spindles of the unit group of spindles, the rotation speeds of the other spindles are influenced by the braking action of the knee brake in such way that the reduction of the rotation speed of a spindle is larger when it is closer to the particular spindles to which the braking action of the knee brake is applied. Nevertheless, because of the relationship thereof to the arrangement of the driving pulleys and tension pulleys utilized in the above-mentioned driving system, it is practically impossible to theoretically analyze the above-mentioned phenomenon of a reduction of the rotation speed of the other spindles by the braking action applied to the above-mentioned particular spindle by means of the knee brake. Accordingly, to find a possible solution to the above-mentioned problem, an experiment has been applied to the above-mentioned unit driving system disclosed in Japanese Unexamined Patent Publication No. Showa 63(1988)-243336, to confirm the influence of the braking action applied to the particular spindle upon the rotation speed of the other spindles of the identical unit group of spindles. It was confirmed that the above-mentioned problem cannot be solved even by the application of a group driving system as mentioned above. Therefore, an object of the present invention is to provide an apparatus for driving spindles of a ring spinning frame wherein a driving system for a unit group of spindles is improved.